Fail-safe System
EF & EC-387prose procedurePage is in the SR (SR20DE/SR20DET) tab of the EF & EC section.
ENGINE AND EMISSION CONTROL SYSTEM DESCRIPTION
Fail-safe System
C.P.U. MALFUNCTION OF E.C.U.
Outline
The fail-safe system makes engine starting possible if there is something malfunctioning in the E.C.U.'s C.P.U. circuit. In former models, engine starting was difficult under the conditions mentioned above. But with the provisions provided in this fail-safe system, it is possible to start the engine.
Fail-safe system activating condition when E.C.U. is malfunctioning
The computing function of the E.C.U. was judged to be malfunctioning. When the fail-safe system activates, i.e. if the E.C.U. detects a malfunction condition in the C.P.U. of E.C.U., the CHECK ENGINE LIGHT on the instrument panel lights to warn the driver.
Engine control, with fail-safe system, operates when E.C.U. is malfunctioning
When the fail-safe system is operating, fuel injection, ignition timing, fuel pump operation, A.A.C. valve operation and radiator fan operation are controlled under certain limitations.
Operation
Fail-safe system operation when C.P.U. is malfunctioning
Fuel injection
OperationSimultaneous injection
Ignition timing
OperationIgnition timing is fixed at the preset value.
Fuel pump
OperationFuel pump relay is "ON" when engine is running and "OFF" when engine stalls.
A.A.C. valve
OperationFull open
Radiator fans
OperationRadiator fan relay "ON"
Cancellation of fail-safe system when E.C.U. is malfunctioning
Activation of the fail-safe system is canceled each time the ignition switch is turned OFF. The system is reactivated if all of the above-mentioned activating conditions are satisfied after turning the ignition switch from OFF to ON.
AIR FLOW METER MALFUNCTION
If the air flow meter output voltage is above or below the specified value, the E.C.U. senses an air flow meter malfunction. In case of a malfunction, the throttle sensor substitutes for the air flow meter.
Though air flow meter is malfunctioning, it is possible to drive the vehicle and start the engine. But engine speed will not rise more than 2,400 rpm in order to inform the driver of fail-safe system operation while driving.
Operation
Air flow meter malfunction operation
Stopped
Starter switchANY
Fail-safe systemDoes not operate
Fail-safe functioning—
Cranking
Starter switchON
Fail-safe systemOperates
Fail-safe functioningEngine will be started by a pre-determined injection pulse on E.C.U.
Running
Starter switchOFF
Fail-safe systemOperates
Fail-safe functioningEngine speed will not rise above 2,400 rpm